Protostar= Human fetus

Fusion Ignition-Main Sequence= Infant through Adulthood
Red Giant=Middle Aged
White Dwarf/Black Hole=Old age/Death
Fetus
Fetus

Proto Star
Proto Star



Adulthood
Adulthood


Fusion Ignition
Fusion Ignition


Red Giant
Red Giant
Middle Aged
Middle Aged


White Dwarf
White Dwarf
Old Aged
Old Aged


1. Why do smaller stars live longer? Larger stars burn up fuel fast to maintain their size.
2. How long will a medium star live in main sequence phase? As stars undergo fusion they gradually follow the paths indicated by the light blue lines until they reach the end of their Main Sequence phase - indicated by the dark blue line.
3. After a star enters "old age," how long will it still live? It depends on the mass of the star.